The present invention relates generally to the field of electrosurgical devices, and more particularly to methods and devices allowing for the monitoring of temperature in regions adjacent, in contact with, and/or surrounding a working end of such electrosurgical devices.
Electrosurgical procedures are extremely common in today's medical practice. For example, present uses of electrosurgical devices include ablation, dissection, resection, coagulation, contraction, or otherwise modification of a broad range of tissues and organs. Thus, general surgery, cosmetic surgery, neurosurgery, laparoscopy, as well as arthroscopic procedures, etc., routinely employ electrosurgical devices and techniques. However, unintended and excessive heating of non-target tissue during the procedure is a common concern in most electrosurgical applications. Such unintended heating of non-target tissue may cause inadvertent necrosis or other damage. Naturally, a medical practitioner employing such devices has a need to know the temperature of the region adjacent to, surrounding, and/or in contact with the working end of the device.
Most electrosurgical cutting devices operate by applying electrical energy to affect tissue. In a first mode, electrical current flows through tissue and as a result of a high current density at the working end of the electrosurgical device (e.g., an electrode), an electrical arc forms across a gap between the electrode and the target tissue. The arc results in rapid tissue heating and vaporization of cellular fluids into steam. In another mode, electrical energy may be directly conducted through tissue, but instead of forming an arc, the resistive properties of the tissue result in heating of the tissue to produce a thermal effect. In yet another mode, as developed by ArthroCare Corporation, Sunnyvale Calif., RF energy is applied to a conductive medium (usually saline), causing a highly focused plasma field to form around the electrodes. This plasma field is comprised of highly ionized particles which have sufficient energy to break organic molecular bonds within tissue. The by-products of this non-heat driven process are elementary molecules and low molecular weight gases. This latter mode is a non-heat driven (the ablation is achieved via the ionized particles) low temperature (surface tissue temperatures 40–70° C.) ablative process and is termed Coblation®. The Coblation® process is discussed more thoroughly below.
In all of the modes described above, a certain amount of heat is generated in the tissue as either a by-product or as a direct result of the mode. This heat conducts through tissue. In the modes which rely on passing electrical current through tissue, electrical current as well as heat conduct through tissue. As a result, heating often occurs not only in or near the target tissue but also in regions surrounding the target tissue. Accordingly, such heating of the surrounding tissue may result in undesirable collateral tissue damage.
Another problem may be found as some surgical procedures require a “wet” field, (i.e., the surgical site is immersed in a fluid medium.) Heat generated by the electrosurgical procedure may accumulate in the fluid medium through transfer of heat into the fluid. In those cases where the fluid medium is a electrically conductive, shorting of the electrode(s) may also occur and result in additional unintended heating in the treatment area. Ultimately, too much additional heating may result in excessive collateral tissue damage.
A number of electrosurgical devices are known that include temperature sensors for sensing temperature in or around a surgical site during a procedure. Such devices typically use electrical temperature sensors, such as thermistors, thermocouples, resistance temperature detectors (RTDs), or fiber optic-based temperature sensors (e.g., U.S. Pat. Nos. 6,293,943 and 6,197,021, both to Panescu et al.).
However, during the procedures described above, a medical practitioner's attention is mainly focused on the operative field either through a viewing monitor (e.g., during a less invasive procedure) or direct visualization (e.g., an open surgical procedure.) Accordingly, there remains a need remains for the medical practitioner to be able to identify the temperature in regions adjacent to, in contact with, and/or surrounding a working end of a electrosurgical devices without solely having to remove his or her attention from the operative field. There also remains a need to provide such a medical device that is disposable and compatible with existing controllers or power supplies.